The UCSC Genome Browser provides the primary point of access to the reference human genome sequence for many tens of thousands of scientists and medical researchers worldwide. It is used over the World Wide Web by more than 5,000 scientists each day, requesting more than a total of 150,000 pages of information. Scientists retrieve direct information about the sequences of human genes, their location in the genome, their normal expression levels in different tissues, the alternatively spliced mRNAs they produce, the protein products they make, and the genetic variations that exist within them in the human population. Users get quick links to other databases at NIH and elsewhere that provide detailed information on each gene's function, its association with human disease, and known disease-causing variants of the gene. [unreadable] [unreadable] Genes make up only approximately 1.5% of our genome. The remaining parts of our genome harbor important non-protein-coding functional elements that control gene expression and other important cellular processes, such as DNA packaging and replication. The UCSC Genome Browser is one of the first tools that allows scientists to begin to explore the vast uncharted landscape of these non-protein-coding functional elements in our genome, and to determine how they affect our health. Like the genes, these other functional elements are evolutionary conserved between different mammals. We identify these elements through their exceptional patterns of evolutionary conservation, using comparisons between the human genome and the genomes of other mammals, including the experimental model organisms, mouse and rat. Our cross-species DNA mappings provide researchers a chance to study individual functional elements in mammalian model organisms that correspond to particular functional elements in the human genome. Through such research, we will learn the functions of both the human genes and the non-coding functional elements in our genome. [unreadable] [unreadable] By mapping the important genetic differences between people and understanding their functional consequences, we lay the groundwork for a future of individualized medicine, where treatment is increasingly tailored to the individual. [unreadable] [unreadable] [unreadable] [unreadable]